This rather wonderful set of interlocking circular stone walls, now largely turf-covered, is the remains of a Romano-British village of first century AD. It was a courtyard settlement – unique to Cornwall, where open yards were included between roundhouses and even within the bigger ones. More here.

Stephen, Sarah and Yvonne loitering on the remains of round stone houses at Carn Euny

It replaced an Iron Age village, with bits dating back a further 500 years, including part of the underground structures ( a fogou, from Cornish for cave). The oldest underground part is a circular corbelled stone room.

Inside the corbelled underground roundhouse at Carn Euny

Later a 20m long passage was linked to it.

Inside the long passage of the fogou. You might ponder on its purpose – nobody knows, but the slabs in the roof are bloody big.